diff --git a/adafruit_wsgi/wsgi_app.py b/adafruit_wsgi/wsgi_app.py
index 249fbdf..a9e78ae 100644
--- a/adafruit_wsgi/wsgi_app.py
+++ b/adafruit_wsgi/wsgi_app.py
@@ -66,8 +66,14 @@ def __call__(self, environ: Dict[str, str], start_response: Callable):
 
         if match:
             args, route = match
-            status, headers, resp_data = route["func"](request, *args)
-
+            try:
+                status, headers, resp_data = route["func"](request, *args)
+            except (ValueError, TypeError) as err:
+                raise RuntimeError(
+                    "Proper HTTP response return not given for request handler '{}'".format(
+                        route["func"].__name__
+                    )
+                ) from err
         start_response(status, headers)
         return resp_data